1. Field of the Invention
The present invention relates to a corrosion inhibitor composition containing a combination of oligoquinoline derivatives and refractory metal oxide.
2. Background of the Prior Art
In deep well gas and oil production there is a need to control the degree of metal corrosion caused by sulfur-compound environments, such as those containing hydrogen sulfide. In these "sour gas" applications, the drilling components and tubing extending into the well, are exposed to acidic environments containing extremely high levels of hydrogen sulfide, combined with carbon dioxide, brine, and hydrocarbons. The iron-containing alloys in these components react with hydrogen disulfide to form ferrous-sulfide phases, e.g., iron sulfide forms on carbon steel. This scale comprises various iron sulfide phases, such as pyrite, marcasite (FeS.sub.2), pyrrhotite (Fe.sub.1-x S), and mackinawite (Fe.sub.1+x S). Ferrous ions are rapidly transported across sulfide phases, such as pyrrhotite, and react with the sulfur containing compound at the outer surface leading to corrosion.
Carbon steel tubes are used for economic reasons since more corrosion resistant materials significantly increase the overall cost of the operation. Many types of corrosion mitigation compounds have been suggested for use as corrosion inhibitors. For example, U.S. Pat. No. 4,028,268 describes a multicomponent inhibitor formulation containing quaternized cyclic nitrogen bases, specific acetylenic alcohols, a specific surface active agent and a formic acid derivative. U.S. Pat. No. 4,387,041, describes an aqueous composition which comprises an acid and 3-dialkylamino-3-(substituted phenyl)-prop-1-yne. U.S. Pat. No. 4,341,657, discloses polymers derived from quinolines and pyridine compounds as being useful components for inhibiting metal corrosion in acidic environments. The polymers, referred to are polyquinolines and polypyridines that have no repeating quinoline or pyridine moieties in their respective structures. U.S. Pat. No. 4,676,834, discloses a corrosion inhibitor composition that includes the reaction product of quinoline, for example, with cycloaliphatic mono-aldehyde. U.S. Pat. No. 4,763,729, describes forming a corrosion resistant layer upon the addition of inhibitors based on refractory metal salts. U.S. Pat. No. 4,880,907 discloses the use of quaternary salts of quinoline oligomers as corrosion inhibitor compositions in the acid environments.
Notwithstanding the teachings in these references, the search for new and improved compounds that are more effective in inhibiting corrosion continues. Particularly desirable are inhibitors that provide corrosion protection against sulfur-containing acidic solutions and show improved high temperature stability. Such compounds would be well-suited for corrosion control in deep well drilling and producing operations.